WASHINGTON (CNN) --Political campaigns went into overdrive Friday with Democratic and Republican leaders, including President Bush, crisscrossing the country to stump for candidates in a blitz for Tuesday's pivotal midterm elections.

Control of the Senate, which Democrats now hold by just one seat, hangs in the balance, and there are several tight gubernatorial races in the country. Given the closeness of numerous races, both sides believe voter turnout is key to victory and are trying to mobilize their respective bases.

Even the first lady, in a rare move, was hitting the campaign trail.

The president, who is visiting 15 states in five days, took part in a rally for two candidates in Pennsylvania and then flew to New Hampshire, where the GOP's nominee for Senate, Rep. John Sununu, is in a tight race with Democratic Gov. Jeanne Shaheen.

In New Hampshire, as in all his campaign stops, Bush spoke of the war on terror and accused the Democratic-controlled Senate of trying to limit his authority.

"We are at war. This and future presidents have to have the ability to put people at the right place at the right time to protect America," Bush said. "I have no doubt that John Sununu supports me on this issue."

Other states on the president's tour, which ends Tuesday with his return to his home state of Texas, include: West Virginia, Kentucky, New Jersey, Tennessee, Georgia, Illinois, Iowa, Missouri, Arkansas, and Florida, where his brother, Gov. Jeb Bush, is fighting for re-election against Democrat Bill McBride.

The president will also spend time in Minnesota and make a return trip to South Dakota.

Clinton campaigns for Democrats

Former President Bill Clinton, who seemed almost as busy campaigning as when he himself ran for office, went to Michigan Friday to promote the candidacy of Jennifer Granholm, who hopes to win election as that state's first female governor, as well as Democratic candidates for the House and Senate.

Clinton praised the diversity of the state's Democratic candidates. "It's an American ticket," he said.

Clinton blamed Republicans as he spoke about the economy, pointing to job losses, a struggling stock market and corporate scandals.

"We have to balance the ideological extremism of the Washington Republicans," he said.

Clinton then left for Maryland, to stump for Lt. Gov. Kathleen Kennedy Townsend, who narrowly trails Rep. Bob Ehrlich, a Republican, in the race for governor there.

One state getting special focus from both parties is Minnesota, where Republican Norm Coleman, the popular former mayor of St. Paul, is locked in a battle with former Vice President Walter Mondale, who stepped in to replace Paul Wellstone after Wellstone's death in a plane crash one week ago.

On Friday, Vice President Dick Cheney and his wife Lynn spoke at a campaign event for Coleman. Wellstone "fought hard for his beliefs and expected others to do the same," the vice president said. "In that spirit, the campaigning continues."

Laura Bush will visit Minnesota amid a three-day campaign blitz of her own that included a stop Friday evening in North Carolina to campaign for Elizabeth Dole, wife of former senator and presidential candidate Bob Dole, in her Senate race against former Clinton aide Erskine Bowles.

Cheney and Mrs. Bush also plan 11th-hour campaign stops in South Dakota, where polls show a dead heat between the candidates for Senate -- Republican Rep. John Thune, personally recruited by Bush, and the Democratic incumbent, Tim Johnson.

Meanwhile, a team of high-powered Democrats including South Dakota's Tom Daschle, the Senate majority leader, launched a three-day, nine-city bus tour with Johnson.

The party in control of the White House usually loses congressional seats in midterm elections. The president is campaigning hard right up to Election Day in an effort to buck that trend.

"You have an obligation in democracy to vote," Bush told the crowd in Pennsylvania.

--White House Correspondent Suzanne Malveaux contributed to this report.